Andrew Albert, husband of New York socialite Annie Churchill, pleaded guilty to felony grand larceny yesterday after he was charged with bilking investors out of $600,000 for his proposed shopping Web site, On1Ave.com. He faces up to 4 1/2 years behind bars. Under the plea deal, if Albert repays his investors $50,000, he’ll serve one to three years — if not, he’ll get the full term. Albert was accused of spending investors’ money on groceries, dog care and a TriBeCa loft. Churchill, the ex-wife of Winston Churchill’s grandson, was not implicated. Albert’s lawyer, Michael Farkas, said, “[He] did try to start a Web site and worked very hard on it for three years.” Churchill declined to comment.